Support for join-condition suggestions after ON

The user types 'SELECT * FROM parenttable p JOIN childtable c on '. We then suggest ['c.parenttableid = p.parenttableid', 'c.createdby = p.createdby', ...] as completions.
The suggestions are FK matches first, then name matches for int columns, then name matches for other columns, sorted by proximity from the cursor to the other table.

Some changes:
    For "JOIN Foo USING(<cursor>)", now only columns present in Foo are suggested.
    For all suggestions after 'ON', now only the tables before the cursor are considered.
    meta[reltype]][relname] goes from being a list of columns to being an OrderedDict {column_name:ColumnMetadata}, where the ColumnMetaData contains the column's name, data type and a list of FKs involving the column. This entails modification of a number of functions dealing with columns.

1 files changed, 14 insertions, 4 deletions

diff --git a/tests/test_pgexecute.py b/tests/test_pgexecute.py
index 9d04da85..c7ed1885 100644
--- a/tests/test_pgexecute.py
+++ b/tests/test_pgexecute.py
@@ -50,18 +50,28 @@ def test_schemata_table_views_and_columns_query(executor):
 
     # tables
     assert set(executor.tables()) >= set([
-        ('public', 'a'), ('public', 'b'), ('schema1', 'c')])
+    ('public', 'a'), ('public', 'b'), ('schema1', 'c')])
 
     assert set(executor.table_columns()) >= set([
-        ('public', 'a', 'x'), ('public', 'a', 'y'),
-        ('public', 'b', 'z'), ('schema1', 'c', 'w')])
+        ('public', 'a', 'x', 'text'), ('public', 'a', 'y', 'text'),
+        ('public', 'b', 'z', 'text'), ('schema1', 'c', 'w', 'text')])
 
     # views
     assert set(executor.views()) >= set([
         ('public', 'd')])
 
     assert set(executor.view_columns()) >= set([
-        ('public', 'd', 'e')])
+        ('public', 'd', 'e', 'int4')])
+
+@dbtest
+def test_foreign_key_query(executor):
+    run(executor, "create schema schema1")
+    run(executor, "create schema schema2")
+    run(executor, "create table schema1.parent(parentid int PRIMARY KEY)")
+    run(executor, "create table schema2.child(childid int PRIMARY KEY, motherid int REFERENCES schema1.parent)")
+
+    assert set(executor.foreignkeys()) >= set([
+        ('schema1', 'parent', 'parentid', 'schema2', 'child', 'motherid')])
 
 @dbtest
 def test_functions_query(executor):